Engine brake lash adjuster device and method

ABSTRACT

A compression brake device and method are provided that include a lash member coupled to a rocker arm. The lash member has a first position that forces opening of the valve when the rocker arm is at the lower position. The brake also includes a lost motion cylinder at least partially defined within the rocker arm. The cylinder is biased towards a position of greatest internal displacement volume. The lost motion cylinder has a first operational mode wherein the lost motion cylinder permits compression thereof such that the ability of the rocker arm to open an exhaust valve is a function of the position of the lash member. The lost motion cylinder has a second operational mode wherein the lost motion cylinder retards compression thereof such that the ability of the rocker arm to open an exhaust valve is independent of the position of the lash member.

CROSS-REFERENCE OR RELATED APPLICATION

The present application claims priority to U.S. provisional patentapplication, Ser. No. 61/859,598, filed Jul. 29, 2013, the disclosure ofwhich is expressly incorporated by reference.

BACKGROUND OF THE DISCLOSURE

This disclosure relates to an exhaust valve actuation mechanism in aninternal combustion engine and an engine brake lash adjuster deviceassociated with the exhaust valve actuation mechanism.

Engine brakes or engine compression brakes take advantage of thecompression and expansion of gases in an engine cylinder to induce aresistance to movement of a piston in the engine cylinder by opening andclosing valves associated with the piston at appropriate times. In orderfor engine brakes to function properly, conventional systems use variousunique components and require certain precise tolerances.

Advantages and features of the embodiments of this disclosure willbecome more apparent from the following detailed description ofexemplary embodiments when viewed in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an engine brake lash adjuster device in accordancewith an exemplary embodiment of the present disclosure.

FIG. 2 is a view of the engine brake lash adjuster device of FIG. 1 in aposition to actuate an exhaust valve.

FIG. 3 is a view of the engine brake lash adjuster device of FIG. 1 witha compression brake actuated.

DETAILED DESCRIPTION OF THE DRAWINGS

According to one embodiment, a compression brake is provided. The brakeincludes a rocker arm pivotable about a rocker arm shaft to selectivelyforce an exhaust valve to an open condition. The rocker arm has a lowerposition, an upper position, and a plurality of positions intermediatethe lower and upper positions. The brake further includes a lash membercoupled to the rocker arm. The lash member is configurable to define aplurality of positions relative to the rocker arm. The lash member has afirst position that forces opening of the valve when the rocker arm isat the lower position. The brake also includes a lost motion cylinder atleast partially defined within the rocker arm. The cylinder is biasedtowards a position of greatest internal displacement volume. The lostmotion cylinder has a first operational mode wherein the lost motioncylinder permits compression thereof such that the ability of the rockerarm to open an exhaust valve is a function of the position of the lashmember. The lost motion cylinder has a second operational mode whereinthe lost motion cylinder retards compression thereof such that theability of the rocker arm to open an exhaust valve is independent of theposition of the lash member.

In another embodiment, a compression brake mechanism is providedincluding: a rocker arm operable to selectively engage an engine valve;a lash member having a plurality of settings that define lash betweenrocker arm movement and engine valve movement; and a lost motionmechanism disposed between the lash member and the engine valve; thelost motion mechanism having a first operational mode and a secondoperational mode, the first operational mode providing an ability toopen an engine valve as a function of the lash member setting, thesecond operational mode providing an ability to open an engine valveindependent of the lash member setting.

In another embodiment, a method of operating an exhaust valve on aninternal combustion engine is provided including: providing a lostmotion cylinder at least partially within a rocker arm operable to openthe exhaust valve; providing a lash member to define a maximum travel ofa piston of the cylinder that defines a first internal volume of thecylinder; providing a seal valve within the rocker arm to selectivelyseal and open the internal volume of the cylinder; closing the sealvalve when the internal volume of the cylinder is a second internalvolume that is greater than a the first volume defined by the lashmember thereby sealing fluid within the cylinder; rotating the rockerarm with the seal valve closed to force open the exhaust valve; andopening the seal valve to release fluid from the cylinder; and rotatingthe rocker arm with the seal valve open such that the cylinder assumesthe first internal volume to force open the exhaust valve.

In yet another embodiment, a method of adjusting lash between an exhaustvalve and a rocker arm on an operating internal combustion engineincluding: providing a rocker arm having a first lash member defining afirst lash amount between the rocker arm and the exhaust valve, thefirst lash amount defining a first point during downward travel of therocker arm at which the exhaust valve is opened; providing a lashvariance member defining a second lash amount between the rocker arm andthe exhaust valve that is smaller than the first lash amount, the secondlast amount defining a second point in the downward travel of the rockerarm at which the exhaust valve is opened, the second point being higherthan the first point; and toggling between the first and second lashamounts within a cycle of the engine.

Referring to FIG. 1, a portion of an internal combustion engine is shownand generally indicated at 10. Engine 10 includes an engine brake orengine compression brake, which provides the ability to retard movementof a crankshaft (note shown) of engine 10 when actuated. Enginecompression brakes provide a valuable capability in a variety ofsituations where a friction brake, such as might be found in conjunctionwith a vehicle wheel, could easily overheat or rapidly wear out. Suchsituations include high loads and steep hills. While engine compressionbrakes provide a valuable capability, they are expensive and complex,requiring additional components and precise component tolerances. Theengine brake of the present disclosure includes an exhaust valveactuation mechanism with a lash adjuster device or mechanism thatprovides the ability to reduce the number of components associated withan engine compression brake and the ability to reduce the tolerances ofcertain components associated with the engine compression brakedisclosed in U.S. Pat. No. 6,253,730, the entire contents of which arehereby incorporated by reference.

Engine 10 includes a rocker arm assembly 12 having a rocker arm body 14,an exhaust valve 16 moved by the action of rocker arm assembly 12, acontrol shaft 18 that extends through rocker arm body 14, a rotatablecamshaft 20, and an engine body 22. The function of rocker arm assembly12 is to control or actuate exhaust valve 16. Thus, rocker arm assembly12 is part of an exhaust valve actuation mechanism. Rocker arm assembly12 includes a reset valve 24, a lash adjuster device 26, a compressionbrake or engine brake hydraulic cylinder or piston 28, and a bearing 30.Reset valve 24 includes a reset pin 32, a detent pin 34, and a resetmember or ball 36, each of which is positioned at least partially withina reset valve cavity 38 formed in rocker arm body 14. Reset valve cavity38 includes a reset valve seat 86 that provides a mating surface forreset ball 36 when reset valve 24 is actuated. Reset valve 24 may alsoinclude a bias spring 40 and a bias spring cup 42 positioned betweenbias spring 40 and reset ball 36. Bias spring 40 and bias spring cup 42bias reset ball 36 toward a proximate end of reset in 32, contactingreset pin 32 during normal or non-compression braking operation ofengine 10. Because this contact prevents reset ball 36 from contactingreset valve seat 86, fluid is able to flow past reset ball 36 towardengine brake piston 28. Reset valve 24 functions to cause the openingand closing of exhaust valve 16 at a time that is independent of theposition of lash adjuster device 26, explained further hereinbelow. Lashadjuster device 26 includes a distal end 84 and a threaded exteriorsurface 74. Engine brake piston 28 is positioned in a body cavity 44formed in rocker arm body 14 and having a body cavity longitudinal axis46. Engine brake piston 28 includes a portion 48 having a sphericalshape on which is positioned a piston shoe 50 having a mating sphericalshape and a shoe contact surface 52, which contacts a proximate end 54of exhaust valve 16. Shoe contact surface 52 may be a planar surface andproximate end 54 mates with the planar surface of shoe contact surface52. Engine brake piston 28 includes an interior surface 56 that forms apiston cavity 58. Interior surface 56 includes an interior distalsurface 70 that extends in a direction that is at an angle to bodycavity longitudinal axis 46 that may be 90 degrees. A piston bias spring80 is positioned between rocker arm body 14 and interior distal surface70 and functions to bias engine brake piston 28 toward piston shoe 50and thus biases piston shoe 50 into contact with exhaust valve 16, whichis biased into the position shown in FIG. 1 by an exhaust valve spring(not shown). Lash adjuster device 26 extends along body cavitylongitudinal axis 46 through a threaded passage 60 formed in rocker armbody 14 into body cavity 44 and then into piston cavity 58. Lashadjuster device 26 is adjustable along body cavity longitudinal axis 46and is secured in position with a jam nut or locking nut 62. Asdescribed further hereinbelow, lash adjuster device 28 functions toactuate exhaust valve 16 during normal operation of engine 10. Bearing30 is positioned on rocker arm body 14 and contacts camshaft 20. Duringoperation of engine 10, camshaft 20 rotates, causing pivotal oscillatingmotion of rocker arm assembly 12 about control shaft 18.

Control shaft 18 includes a control shaft oil passage 64, which connectswith a first rocker arm oil passage 66 formed in rocker arm body 14 thatfluidly connects to reset valve cavity 38. Rocker arm body 14 furtherincludes a second rocker arm oil passage 68 that extends between resetvalve cavity 38 and body cavity 44, fluidly connecting reset valvecavity 38 to body cavity 44. An engine oil pump (not shown) thatprovides oil pressure for various engine functions, such as lubrication,also provides pressure to the oil that flows into control shaft oilpassage 64, which then flows into first rocker arm body oil passage 66.Under normal engine operating conditions, the oil in control shaft oilpassage 64 and first rocker arm body oil passage 66 provides lubricationto the various components fluidly connected to control shaft oil passage64 and rocker arm body oil passage 66. These passages provide a controlfunction to certain components of rocker arm assembly during enginecompression braking, described further hereinbelow.

The longitudinal position of lash adjuster device 26 is set daringassembly of engine 10, and because of the ability to identify thedistance exhaust valve 16 needs to open empirically, setting the lash iseasily accomplished through an automated process. With rocker armassembly 12 in the position shown in FIG. 1, and with jam nut 62 in aposition to permit movement of lash adjuster device 26, lash adjusterdevice 26 is driven or moved longitudinally downward toward interiordistal surface 70 of engine brake piston 28. Once lash adjuster device26 contacts interior distal surface 70 of engine brake piston 28, thedrive torque to move lash adjuster device 26 increases non-linearly,which indicates that lash adjuster device 26 has contacted interiordistal surface 70 of engine brake piston 28. Once an automated assemblymechanism (not shown) detects the contact between lash adjuster device26 and interior distal surface 70, lash adjuster device 26 is movedlongitudinally away from interior distal surface 70 of engine brakepiston 28 by a predetermined amount. Once movement of lash adjusterdevice 26 by the predetermined amount has been accomplished, jam nut 62is secured against a jam nut contact surface 72 of rocker arm body 14 tolock lash adjuster device 26 in a fixed position. In the exemplaryembodiment, lash adjuster device 26 includes exterior threaded surface74 that mates with a similar thread formed in threaded passage 60 ofrocker arm body 14, and longitudinal movement of lash adjuster device 26is accomplished by rotating lash adjuster device 26 about body cavitylongitudinal axis 46, which moves lash adjuster device 26 longitudinallyalong body cavity longitudinal axis 46. The ability to set the positionof lash adjuster device 26, which determines when exhaust valve 16 isactuated, reduces the tolerances that would otherwise be required in thefabrication of rocker arm body 14.

During normal operation of engine 10, as camshaft 20 rotates, camshaft20 contacts rocker assembly bearing 30. Camshaft 20 includes a camprofile 76 that causes oscillating pivotal motion of rocker arm assembly12 about control shaft 18. In the exemplary embodiment, cam profile 76of camshaft 20 is shown as having only one lift event per revolution ofcamshaft 20. It should be understood that camshaft 20 can have anynumber of lift events to achieve various performance conditions, whichincludes control of exhaust emissions. Reset pin 32 includes a recess,undercut, or engaging feature 78, that is engaged by detent pin 34during normal operation of engine 10. The position of detent pin 34 ismaintained by a bias spring mechanism (not shown), until a solenoid orother actuation mechanism (not shown) moves detent pin 34 to a positionwhere detent pin 34 disengages from reset pin 32, which permits resetpin 32 to move toward a contact pad 80 formed on engine body 22, asshown in FIG. 3, which permits reset valve 24 to close, describedfurther hereinbelow.

As rocker arm assembly 12 rotates in a counterclockwise directionthrough contact of bearing 30 with cam profile 76, as shown in FIG. 2,engine brake piston 28 compresses piston bias spring 82 until interiordistal surface 72 of engine brake piston 28 contacts lash adjusterdevice 26. This actuation of exhaust valve 16 is sometimes called lostmotion. Further counterclockwise motion of rocker arm assembly 12 movesexhaust valve 16, causing exhaust valve 16 to open, which permitsexhaust gases to escape from engine body 22 in a known manner. Camprofile 76 of camshaft 20 is configured to provide for rapid movement oflash adjuster device 26 toward interior distal surface 70 of enginebrake piston 28 until distal end 84 of lash adjuster device 26approaches interior distal surface 70 of engine brake piston 28, atwhich point cam profile 76 provides a decreased velocity of lashadjuster device 26 to minimize the impact of lash adjuster device 26with interior distal surface 70 of engine brake piston 28. By reducingthe impact, the life and reliability of lash adjuster device 26 andengine brake piston 28 are extended.

When the engine brake function is engaged, as shown in FIG. 3, detentpin 34 is moved to disengage from engaging feature 78, permitting resetpin 32 to move longitudinally toward contact pad 80 of engine body 22.Oil pressure present in rocker arm oil passage 66 and reset valve cavity38 forces reset pin 32 longitudinally toward contact pad 80, whichpermits reset valve ball 36 to move toward and contact reset valve seat86 by the action of bias spring 40, trapping oil in second rocker armoil passage 68 and in body cavity 44. With oil trapped in second rockerarm oil passage 68 and body cavity 44, engine brake piston 28 is unableto move as rocker arm assembly 12 moves in a counterclockwise direction,because engine brake piston 28 is unable to compress the trapped oil,and thus movement of rocker arm assembly 12 causes engine brake piston28 to move exhaust valve 16 sooner than would otherwise happen bycontact of lash adjuster device 26 with interior distal surface 70 ofengine brake piston 28. To disengage the give compression brake, detentpin 34 is moved along its axis to engage with recess 78 reset pin 32 asreset pin 32 moves toward reset ball 36 through contact with contact pad80. As reset pin 32 moves off reset valve seat 86, oil compressed byengine brake piston is able to flow from body cavity 44 into secondrocker arm oil passage 68, and then through reset valve cavity intofirst rocker arm oil passage 66, and then into control shaft oil passage64, permitting engine brake piston 28 to move toward lash adjuster 26,restoring normal, or non-braking operation, of rocker arm assembly 12.

Thus, lash adjuster device 26 in combination with reset valve 24 permitsthe ability o combine functions in rocker arm assembly 12 to providemovement of exhaust valve 16 during operation of engine 10 as well as adifferent timing of the motion of exhaust valve 16 during engine brakingevents. By combining two functions in rocker arm assembly 12, cost andcomplexity of engine 10 is reduced significantly while providing anengine compression brake for engine 10.

While various embodiments of the disclosure have been shown anddescribed, it is understood that these embodiments are not limitedthereto. The embodiments may be changed, modified and further applied bythose skilled in the art. Therefore, these embodiments are not limitedto the detail shown and described previously, but also include all suchchanges and modifications.

1. A compression brake including: a rocker arm pivotable about a rockerarm shaft to selectively force an exhaust valve to an open condition,the rocker arm having a lower position, an upper position, and aplurality of positions intermediate the lower and upper positions; alash member coupled to the rocker arm, the lash member beingconfigurable to define a plurality of positions relative to the rockerarm, the lash member having a first position that forces opening of thevalve when the rocker arm is at the lower position, and a lost motioncylinder at least partially defined within the rocker arm, the cylinderbiased towards a position of greatest internal displacement volume, thelost motion cylinder having a first operational mode wherein the lostmotion cylinder permits compression thereof such that the ability of therocker arm to open an exhaust valve is a function of the position of thelash member, the lost motion cylinder having a second operational modewherein the lost motion cylinder retards compression thereof such thatthe ability of the rocker arm to open an exhaust valve is independent ofthe position of the lash member.
 2. The engine of claim 1, wherein thesecond operational mode of the lost motion cylinder is an enginecompression braking mode and the first operational mode of the lostmotion cylinder is a non-engine compression braking mode.
 3. The engineof claim 1, further including a seal valve within the rocker arm that,when closed, places the lost motion cylinder into the second operationalmode.
 4. The engine of claim 3, wherein the seal valve is biased towardsa closed position.
 5. The engine of claim 3, wherein the seal valveincludes an actuator that abuts a portion of an engine when the rockerarm is in the lower position to place the seal valve in the openposition and to place the lost motion cylinder in the second operationalmode.
 6. The engine of claim 3, further including a lock that holds theseal valve in the open position.
 7. The engine of claim 6, furtherincluding a solenoid that selectively releases the lock.
 8. Acompression brake mechanism including: a rocker arm operable toselectively engage an engine valve; a lash member having a plurality ofsettings that define lash between rocker arm movement and engine valvemovement; and a lost motion mechanism disposed between the lash memberand the engine valve; the lost motion mechanism having a firstoperational mode and a second operational mode, the first operationalmode providing an ability to open an engine valve as a function of thelash member setting, the second operational mode providing an ability toopen an engine valve independent of the lash member setting.
 9. Thebrake mechanism of claim 8, further comprising an engine valve uponwhich the lash member acts, wherein the engine valve is an exhaust valveand the second operational mode provides engine compression braking. 10.The brake mechanism of claim 8, further including at least one sealvalve within the rocker arm, the at least one seal valve being operablesuch that the second operational mode of the lost motion mechanism trapsfluid within a portion of the rocker arm.
 11. The brake mechanism ofclaim 10, wherein the trapping of fluid prevents loss of motion by thelost motion mechanism.
 12. The brake mechanism of claim 10, furtherincluding a lock operable to hold the lost motion mechanism in the firstoperational mode.
 13. The brake mechanism of claim 12, wherein the sealvalve is biased to a closed position corresponding to the secondoperational mode, and releasing the hold provided by the lock permitsthe biasing of the seal valve to assume the closed position.
 14. Thebrake mechanism of claim 13, further including a reset pin that isselectively locked by the lock, the reset pin having a first portionextending outside of the rocker arm, force applied to the first portionurging opening of the seal valve.
 15. The brake mechanism of claim 8,wherein the lost motion mechanism includes a cylinder, the firstoperational mode permitting egress of fluid from the cylinder, thesecond operational mode preventing egress of fluid from the cylinder.16. The brake mechanism of claim 15, wherein the lash member provides alimit on the travel of the cylinder.
 17. The brake mechanism of claim15, wherein the lash member provides a limit on the minimum interiorvolume of the cylinder.
 18. The brake mechanism of claim 8, wherein thebrake is operational on a 4-stroke engine, wherein the lost motionmechanism is in the first operational mode during an exhaust stroke andthe lost motion mechanism, when in the second operational mode, releasesfluid compressed during a compression stroke.
 19. The brake mechanism ofclaim 8, wherein the brake mechanism is part of an internal combustionengine.
 20. A method of operating an exhaust valve on an internalcombustion engine including: providing a lost motion cylinder at leastpartially within a rocker arm operable to open the exhaust valve;providing a lash member to define a maximum travel of a piston of thecylinder that defines a first internal volume of the cylinder; providinga seal valve within the rocker arm to selectively seal and open theinternal volume of the cylinder; closing the seal valve when theinternal volume of the cylinder is a second internal volume that isgreater than a the first volume defined by the lash member therebysealing fluid within the cylinder; rotating the rocker arm with the sealvalve closed to force open the exhaust valve; opening the seal valve torelease fluid from the cylinder; and rotating the rocker arm with theseal valve open such that the cylinder assumes the first internal volumeto force open the exhaust valve.
 21. The method of claim 20, whereinrotating the rocker arm with the seal valve closed causes opening of theexhaust valve.
 22. A method of adjusting lash between an exhaust valveand a rocker arm on an operating internal combustion engine including:providing a rocker arm having a first lash member defining a first lashamount between the rocker arm and the exhaust valve, the first lashamount defining a first point during downward travel of the rocker armat which the exhaust valve is opened; providing a lash variance memberdefining a second lash amount between the rocker arm and the exhaustvalve that is smaller than the first lash amount, the second last amountdefining a second point in the downward travel of the rocker arm atwhich the exhaust valve is opened, the second point being higher thanthe first point; and toggling between the first and second lash amountswithin a cycle of the engine.
 23. The method of claim 22, wherein thelash variance member includes a hydraulic piston.
 24. The method ofclaim 23, wherein the hydraulic piston includes a displacement, thedisplacement being limited by the first lash member to define a firstdisplacement.
 25. The method of claim 23, wherein the second lash amountis defined by a second displacement of the hydraulic piston that isgreater than the first displacement.